# coding=utf-8book_list_in_library = []ready_borrow_book_list = []borrowed_book_list = []menu_info = """input 1:add new book to libraryinput 2:borrow book from libraryinput 3:list all books in libraryinput 4:list all borrowed books in libraryinput 5: list current books in libraryinput 6:lend a book"""def add_book():    global book_list_in_library    global ready_borrow_book_list    book_name = raw_input("please input the book name to add:")    book_list_in_library.append(book_name)    ready_borrow_book_list.append(book_name)def borrow_book():    global ready_borrow_book_list    global borrowed_book_list    while 1:        book_name = raw_input("please input the book name to borrow:")        if book_name in ready_borrow_book_list:            ready_borrow_book_list.remove(book_name)            borrowed_book_list.append(book_name)            print "borrow book done!"            break        else:            print "the book you borrow does not exist,try again!"def lend_book():    global ready_borrow_book_list    global borrowed_book_list    while 1:        book_name = raw_input("please input the book name to lend:")        if book_name in borrowed_book_list:            borrowed_book_list.remove(book_name)            ready_borrow_book_list.append(book_name)            print "lend book done!"            break        else:            print "the book you lend does not exist,try again!"while 1:    print menu_info    command = raw_input("please input your command:")    if command == "1":        add_book()        print ready_borrow_book_list        print book_list_in_library        continue    if command == "2":        borrow_book()    if command == "3":        print "all books are :", book_list_in_library    if command == "4":        print "borrowed books are :", borrowed_book_list    if command == "5":        print "current books in library are :", ready_borrow_book_list    if command == "6":        lend_book()    if command == "q":        break

心得：把功能分解，一个方法一个实现